Conventionally, an electrolysis solution for an electrolytic capacitor obtained by dissolving organic acid, inorganic acid, or salts thereof as an electrolyte in an organic solvent has been used.
Among electrolysis solutions, development of an electrolysis solution for an electrolytic capacitor, which has high electric conductivity and spark voltage, has been carried out actively because electric conductivity is directly related to loss in an electrolytic capacitor, impedance properties, and the like.
As disclosed in Patent Literature 1, as additives for improving spark voltage, for example, sulfamic acid, suberic acid, dodecyl phosphate, porous polyimide, and the like are known. All of these additives have excellent initial spark voltage but soon deteriorate during use, and therefore have a problem of poor heat resistance.
Patent Literature 2 discloses technology in which spark voltage is improved by using colloidal silica as inorganic oxidized colloidal particles in order to improve spark voltage while high electric conductivity is maintained. While an electrolysis solution containing colloidal silica has high initial spark voltage, the electrolysis solution has a problem in that it gels during use and short-circuits and thus has poor heat resistance.
As mentioned above, an electrolysis solution for an electrolytic capacitor having high spark voltage and excellent electric conductivity and heat resistance to spark voltage, and an electrolytic capacitor using the electrolysis solution, have been demanded.